Question about stabbing a distributor

[olddog]

Originally Posted by Ohio Ken

Being that it is a mechanical advance, it must be affecting my idle timing . As I said in first post. I did verify that at full advance at 3000RPM is around 34. And she starts great and revs great. So I should be good to go. I just didn't understand why I am pointing at 20 (makes sense that the mechanical advance may be why.
Thanks to all for your input
Ken

On a typical vacuum advance set up you set the initial at 10, with vacuum disconnected. The vacuum pulls in ~15-20 deg. The mechanical pulls in ~20-25 deg. At WOT the vacuum does nothing and the mechanical controls the WOT timing. At light loads, the vacuum pulls in the extra timing needed. With the vacuum connected (before the ported vacuum abomination to meet emissions) 25-30 deg at idle was typically what the engine needed.

A street engine will run like crap, if you set initial timing at 10, with no vacuum advance. So what they did was set the initial at 20. Then they set the mechanical to advance 14. 20+14=34. This is robbing Peter to pay Paul, but it half ass works. The problem is if you open the throttle below ~2000 rpm you will have too much timing, and the engine may well go into detonation, destroying it. So do not go WOT at low rpm with this distributor! Additionally you do not have enough timing at light loads. Your engine runs hotter, makes less power, and wastes fuel. The emissions suck, too. So you have an engine that only runs well at WOT and higher rpms. Everyplace else is a half ass compromise, but it's cool cause racers do it!